Have you ever wondered how our physical bodies can produce the non-physical phenomenon we call the mind? Even if you believe in a non-physical soul or consciousness, you still have to ask: What is the relationship between our physical body and our immaterial soul? How do they interact? How does something physical affect something non-physical? Similarly, how can something non-physical like the mind affect our physical bodies? If you believe in a God who created the world but is not physical, you should ask yourself: How could a non-physical creator generate physical nature, and how does she/he interact with or influence it? Needless to say, these questions have bothered philosophers for as long as philosophy has existed.
A straightforward solution, which is gaining more support from neuroscience and modern psychology, comes from materialists like Epicurus and the Carvakas. They argue that matter is the ultimate substance of the universe, and mind is simply a derivative of matter. Most materialists, including scientific realists, adopt this view because they do not accept the existence of anything that cannot be scientifically examined. This constraint inevitably makes matter the fundamental reality of the world. Advances in AI, especially large language models, seem to support this view, as some higher-order mental functions can now be performed by machines.
On the other hand, idealists like Berkeley and Leibniz consider matter to be a byproduct of the mind, making mind the fundamental reality of the universe. In dreams, you experience a material world created by your mind. Thus, you don’t really need physical objects to exist outside yourself to perceive a material world. In virtual reality as well, you can experience and interact with a material world that doesn’t actually exist. If your mind is provided with different types of sensations like visual signals, auditory signals, touch, etc., you end up perceiving matter and a world that exists only in your mind.
It’s impossible to discuss the mind-body problem without mentioning Descartes. He proposed the famous theory of Cartesian dualism, treating mind and matter as two entirely independent fundamental realities. Descartes recognized that dualism demands an explanation of how these two independent realities influence and interact with each other. For example, some people smash a plate when they are extremely angry, while something physical like falling off your chair at work can dampen your mood. He was unable to provide a satisfactory explanation for how this interaction occurs, which made his theory of interactionism a major target for criticism by later philosophers.
Spinoza explicitly rejected the Cartesian philosophy of interactionism. While others struggled to identify a causal bridge between the mental and the physical, Spinoza proposed a framework that integrated neutral monism with psychophysical parallelism. Let’s unpack these terms:
- Neutral monism: Spinoza maintained that there exists only one neutral, infinite, and indivisible substance, which he called God or Nature, and that all individual entities, such as humans or rocks, are merely modified expressions of this single reality. While the substance possesses infinite attributes, we are only capable of perceiving two: mind (thought) and matter (extension). Everything in existence, from pebbles to humans, being a mode of this infinite substance, has both a physical and a mental aspect. For example, gravity can be understood through abstract mathematical equations (mental aspect) or observed through its physical effects on objects.
- Psychophysical parallelism: Using a geometric analogy, he described the two attributes as running in parallel, meaning that mind and matter are independent but always coordinated. By independent, he means that changes in one don’t impact the other attribute, but because they are also coordinated, changes in one are always accompanied by a necessary change in the other. This allows him to deny a causal link between the two attributes, while maintaining that we observe simultaneous changes happening in both. If you synchronize two clocks to show the same time, they will continue to display the same time, but not because they are affecting each other.
To illustrate this more clearly, imagine a high-definition digital photo stored on a hard drive. At its most basic level, the file consists of a sequence of 1s and 0s, magnetic charges that are inherently neutral, being neither “redness” nor “voltage” in themselves. This single file can be accessed in two ways: through a text editor or an image viewer. In a text editor, you see the “physical” data represented as binary or hex code. In an image viewer, you see a sunset, representing the “qualitative” or mental experience of that same data. In this digital analogy, altering the underlying binary code instantly changes both the text representation and the visual image. However, it would be illogical to search for a “causal” link between the text and the picture, as they are simply different versions of the same data. Similarly, Spinoza argued that the correlation between mental and physical events does not imply that one causes the other. By rejecting interactionism, he posited that mind and matter remain independent yet perfectly coordinated. A change in one attribute is necessarily and harmoniously reflected in the other. Ultimately, Spinoza replaced the puzzle of mind-body interaction with a deterministic system, where all events arise from the necessary nature of the one, infinite substance.
Many other metaphysical frameworks attempt to solve the mind-body problem, but most are simply variations of the ones already discussed.
Now, let’s look at what psychology tells us. Since we are moving from philosophy to science, let’s follow scientific principles and define the object we are studying to remove any subjectivity. What is mind? It’s easy to discuss and draw conclusions about the mind until someone asks us to define it precisely, without vagueness. If I ask you to define the heart, you can describe it using its location, composition, function, and how it works. We are still trying to figure out where the mind is, what it is made of, and how it does what it does. Thus, we can only include the functions of mind in its definition. We can then ask whether something within us already performs these functions, or if we truly need an immaterial entity to explain the mind’s role in our lives.
The most widely accepted framework for categorizing functions of the mind is the Tripartite Model, often summarized by the “ABC” of psychology: Affect (Feeling), Behavior (Acting), and Cognition (Thinking). Psychologists generally divide mental functions into these three faculties:
- Cognition (The “Knowing” Function): Cognition refers to how we acquire, process, store, and use information. It includes processes like perception, memory, learning, decision making, thinking, and reasoning.
- Affect (The “Feeling” Function): Affect encompasses everything related to the internal “weather” of the mind, that is, our feelings and evaluations of the world.
- Conation (The “Willing” Function): Conation refers to the will, motivation, and drive that turn thoughts and feelings into action.
Thus, mind is defined as the set of mental processes that enable perception, thought, emotion, memory, motivation, and behavior. Psychologists also emphasize that much of the mind lies outside our conscious awareness, operating automatically to influence our actions and experiences.
Now that we have a clear definition of mind, let’s see if there is anything within us that can be linked to these functions. The answer is a resounding yes. Our brain, a physical organ made of matter, is associated with all these functions. Rather than detailing how each brain structure performs these functions, let me pose a simple question: If someone damaged your brain, would you expect your perception, thought, emotion, memory, motivation, and behavior to remain the same?
Even without the advanced tools available to modern neuroscientists, we could answer this question just by looking at people with brain injuries. The classic example is Phineas Gage, a railroad worker who survived a severe brain injury when an iron rod pierced through his skull. Before the accident, Gage was known to be a responsible and hardworking individual. However, after the injury, his personality changed dramatically; he became impulsive, irritable, and unreliable. Thus, if you think of yourself as calm and stoic, damaging certain parts of your brain could make you aggressive or anxious.
Phineas Gage also reported increased sex drive after his accident, indicating that brain damage can affect motivation and desires as well. These observations strongly suggest that our mental functions are closely tied to the physical state of our brain. We also know that damage to the brain can lead to memory formation problems (like in Alzheimer’s disease), difficulties in language (like in aphasia), and problems in perception (such as hallucinations).
Another interesting story comes from Oliver Sacks, who described the case of a teenager named Greg F. Once extremely angry and volatile, Greg joined the Hare Krishna temple and, over time, became remarkably calm, peaceful, and constantly smiling. His swami at the temple regarded him as a spiritually enlightened soul. Greg mentioned experiencing vision problems, which his teachers interpreted as “inner divine light.” When Greg’s parents visited the temple, his father was shocked by the dramatic change and even described Greg’s smile as “stupid.” It was later discovered that Greg had a massive brain tumor that had destroyed significant brain structures, including his optic nerves, resulting in blindness. The tumor also caused severe short-term memory loss and emotional changes, leaving him in a “bland, placid, emptied of all feeling” state.
Your cognitions, affects, and conations are all deeply influenced by your brain. We don’t need to be neuroscientists to see that damaging the brain will change how we think, feel, and act. Your wishes, desires, motivations, and drives all result from your brain’s functioning. The above cases illustrate that changes in the brain can lead to significant alterations in mental functions. Thus, based on the definition of mind we agreed on, we can confidently say that none of those functions require an immaterial entity to be performed. Everything that mind does can be explained by the physical brain. Your mind is what your brain does.
I’d like to end this blog with a powerful quote from Francis Crick, the co-discoverer of the structure of DNA, also called the “Astonishing Hypothesis”: You, your joys and your sorrows, your memories and your ambitions, your sense of personal identity and free will, are in fact no more than the behavior of a vast assembly of nerve cells and their associated molecules.
Thank you for reading!